1. Field of the Invention
The invention relates to automatic transmission testers, specifically to such test instruments which test solenoids and pressure switches after they have been removed from an automatic transmission.
2. Description of Prior Art
The shifting and fluid pressure regulation of the modem automatic transmission is controlled by fluid control devices called shift solenoids, pressure regulation solenoids called force motor solenoids, and pressure switches. These devices supply and regulate the flow of fluid to perform various functions of the automatic transmission. Solenoids are devices consisting of an electrical coil which, when a given amount of electrical current flows through it, activates a valve to control the flow of transmission fluid. A pressure switch is a device containing an electrical switch which is activated when fluid pressure is applied. A defective solenoid or pressure switch will cause an automatic transmission to malfunction. When a solenoid becomes defective, the usual cause is an obstruction to fluid flow in the solenoid valve from fluid contamination or to an open or short circuit in the solenoid coil. Usually, a solenoid is identified as being faulty by a commercially available computerized diagnostic device as suggested by U.S. Pat. No. 5,521,818 to Palansky (1995). This diagnostic device is used to identify faults in an automatic transmission while it is still mounted and operating in a vehicle. Thus there is a need for a test instrument which allows a solenoid, suspected of being faulty as indicated by the above diagnostic device, to be removed from the automatic transmission and individually tested. The repaired or replacement solenoid can then be tested by the test instrument before being remounted in the transmission.